Magnetic closure

ABSTRACT

A closure device for an opening having a boundary defined by a border of a flexible panel and a border along another member, which may be a flexible panel, includes a plurality of spaced permanent magnets that run downwardly along one of the borders from an apex where the two borders join. Each of the permanent magnets includes strong magnetic pole faces on a surface abutting the boundary to establish a magnetic force across the boundary in a plane substantially parallel to a plane in which the flexible panel lies while the opening is closed. The permanent magnets have weak magnetic poles on the opposite surface thereof, remote from the boundary. On the other border, a plurality of spaced magnetic force attractive elements are provided in positions aligned with the permanent magnets. The elements may be either second permanent magnets or members of relatively high magnetic permeability. As the flexible panel moves about the apex by gravity from an open condition toward a closed position the magnetic forces bring and hold successive segments of the two borders in abutting relationship. The portions of the border that are closer to the apex generally come into abutting relationship with each other prior to the portions of the border that are farther from the apex.

United States Patent [191 Serbu [11] 3,827,019 1 July 30, 1974 1 1 MAGNETIC CLOSURE [76] Inventor: Gideon P. Serbu, Box 280, Rt. 1,

Accokeek, Md. 20607 [22] Filed: Feb. 21, 1973 [21] Appl. No.: 334,234

Primary Examiner-George Harris Attorney, Agent, or Firm-Lowe, King and Price [57] ABSTRACT A closure device for an opening having a boundary defined by a border of a flexible panel and a border along another member, which may be a flexible panel, includes a plurality of spaced permanent magnets that run downwardly along one of the borders from an apex where the two borders join. Each of the permanent magnets includes strong magnetic pole faces on a surface abutting the boundary to establish a magnetic force across the boundary in a plane substantially parallel to a plane in which the flexible panel lies while the opening is closed. The permanent magnets have weak magnetic poles on the opposite surface thereof, remote from the boundary. On the other border, a plurality of spaced magnetic force attractive elements are provided in positions aligned with the permanent magnets. The elements may be either second permanent magnets or members of relatively high magnetic permeability. As the flexible panel moves about the apex by gravity from an open condition toward a closed position the magnetic forces bring and hold successive segments of the two borders in abutting relationship. The portions of the border that are closer to the apex generally come into abutting relationship with each other prior to the portions of the border that are farther from the apex.

13 Claims, 6 Drawing Figures PAIENIEDJUL 30 1974 SHEET 1 BF 2 asnav A AVAVAVAVA FIELD OF INVENTION The present invention relates generally to closure devices and more particularly to a magnetic closure de vice wherein a magnetic force is established in a plane substantially parallel to the plane of a flexible panel having an edge defining a border of the closure.

BACKGROUND OF THE INVENTION Many devices have been developed for closures for openings having a longitudinally extending boundary that is defined by a border of at least one flexible panel member. Such closure devices have typically been in the form of buttoms, buckles, clasps and slide fasteners, particularly of the zipper type. In order for an object to move through an opening formed by a typical prior art closure device of the above-mentioned type, the closure device must be mechanically manipulated throughout the length of the opening. After the object has moved through the opening, the closure device must again be mechanically manipulated. For certain types of openings, such as openings through the flaps or front panels of a tent, where it is necessary to open and close a pair of closure devices generally extending at right angles to each other each time ingress and egress to the tent occurs, the mechanical manipulation can be time consuming and bothersome. For a tent closure, where it is imperative to provide as effective a closure as possible at all times in order to keep insects from the interior of the tent, mechanical manipulation of the closure is frequently difficult because articles carried in both-hands are frequently brought through the closure device. I

In an attempt to avoid the mechanical manipulation required of typical prior art closure devices of the type specified supra, magnetic closure devices have been proposed. The proposed magnetic closure devices have generally involved permanent magnets arranged so that a magnetic force is provided in a plane at right angles to the plane of a panel forming the closure. The magnetic force is directed toward a corresponding magnetic attractive member on a second panel; corresponding elements may be either a permanent magnet or an element having high magnetic permeability. The two panels are thereby in generally abutting relationship with an overlapping portion in the region where the permanent magnet holds the two panels together. Because of the overlapping region between the two panels, easy access through the opening in both directions is not provided. If one panelhas two degrees of freedom of movement so that its faces can contact one or the other face of the other panel, the closure may not be effected at all. This is particularly true if both pole areas are on the same face of the permanent magnet, since one face of such permanent magnets is generally polarized to a much greater extent than the other face. If the permanent magnet is polarized through its width, so that the two faces thereof are oppositely polarized, a proper seal may not be provided because magnets along different portions of the closure region might have a tendency to cause opposite faces of the two panels to abut against each other. Hence, along a first portion of the seal the abutting faces of the two panels could be one pair of faces and along a second portion of the seal the abutting faces couldbe the faces on the opposite sides of the panels. In such a situation, a hole would be left in a transition region between the first and second portions of the seal.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention the overlap problems of prior art magnetic closure devices are avoided by including permanent magnet means that establishes magnetic forces across a boundary of the closure in a plane substantially parallel to a plane ofa first flexible panel. Magnetic force attractive means on a border of a second panel or member responds to the magnetic forces to hold the two borders in abutting relationship without overlap between the panels. Because the borders are in abutting, non-overlapping relationship, movement of an object through the closure device in either direction is facilitated.

If the two borders are vertically disposed they have an apex at an upper portion thereof. Thereby, when the flexible panel is being closed, it returns initially by gravity toward the other panel and the permanent magnets provide horizontal forces that thereafter bring and hold aligned segments of the two borders in contact. Successive portions of the two borders contact each other, with the portions closest to the apex generally contacting each other before the portions more remote from the apex.

By providing'the magnetic force in a plane substantially parallel to the plane of the flexible panel and utilizing bar magnets having poles at opposite ends of the bar on a front face abutting the boundary, the front faces of the permanent magnets always provide the strong magnetic field necessary to establish alignment of the panels across the boundary. Alignment is thereby achieved regardless of the relative initial position of the faces of the flexible panel relative to the faces of the other member. This is in contrast with the prior art magnetic closures, as discussed supra.

Another feature of the invention relates particularly to closures having boundaries defined by a pair of intersecting slits that run in different directions, such as in a tent where there are a downwardly extending center slit and a horizontally extending slit that runs in proximity to the ground from the center slit toward the outer periphery of the tent. In accordance with this feature, the center slit is closed by the previously discussed mechanism while the horizontally extending slit is closed by a vertically directed magnetic force formed by a permanent magnet included either in a threshold running in the horizontal direction or in the horizontally extending portion of the panel. The vertical magnetic force across the horizontally extending slit extends in a direction parallel to the plane of the flexible panel which engages the threshold. In operation, as the closure is sealed along the vertical slit in response to the gravitational and horizontally directed magnetic forces, the panel is secured in situ to the threshold by the vertically directed magnetic forces established between magnetic elements that extend along the horizontally extending slit.

To enable the flexible panel to retain its flexibility, the magnetic elements therein, whether they be permanent magnets or elements of high magnetic permeability, are arranged so that there are gaps between the magnetic fields of adjacent magnets. The gaps can be provided by spacing the permanent magnets or magnetic elements of high magnetic permeability, or by providing a magnetic element of high magnetic permeability that is continuous but inherently provides magnetic field gaps therein, such as a link chain.

If one of the members forming a boundary of the closure is rigid, such as the threshold of a tent, the magnetic force which is parallel to the plane of the flexible panel, can be provided by mounting in the rigid member an elongated, single piece permanent magnet having magnetic poles on opposite faces of the magnet.

It is, accordingly, an object of the present invention to provide a new and improved magnetic closure device.

Another object of the invention is to provide a new and improved magnetic closure device wherein movement of an objectthrough the closure device is provided with equal facility in either direction and the device automatically closes after the object has moved through an opening of the closure device.

A further object of the invention is to provide a new and improved magnetic closure which can be opened without manual manipulation of the closure structure.

An additional object of the invention is to provide a new and improved magnetic closure device which can be opened by merely applying a force to a flexible panel that has an edge defining a border of a boundary of an opening of the closure device, and wherein the closure device automatically returns to a closed position without manual manipulation.

An additional object of the invention is to provide a new and improved magnetic closure device for vertically extending openings, having a boundary defined by a vertically extending border of a flexible panel.

An additional object of the invention is to provide a new and improved closure device for a flexible panel member havinga pair of intersecting edges that run in different directions and which define a boundary of an opening.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OFTHE DRAWING opening, in accordance with a preferred embodiment;

FIG. 4 is a side sectional view, taken through the line 4-4, FIG. 2, illustrating a threshold closure device, in combination with a portion of the vertical closure structure;

FIG. 5 is a view illustrating the invention in conjunction with a tent; and

DETAILED DESCRIPTION OF THE DRAWING Reference is now made to FIGS. 1-4 of the drawing wherein there is illustrated a pair of flexible, nonmagnetic panels 11 and 12 that have abutting, nonoverlapping, vertically extending edges 13 and 14 which are closed by the closure device of the present invention. Panels 11 and 12 also include horizontally extending edges 15 and 16 which are brought into abutting relationship with fixed threshold structure 17 by the closure device of the present invention. Edges 15 and 16 extend outwardly from center line 18 along which edges 13 and 14 abut when the closure device is closed.

The closure device for edges or borders l3 and 14 comprises a plurality of spaced permanent bar magnets 21 and'and 22 which are fixedly mounted by suitable means, such as by bonding or impregnation, in hems 23 and 24 thatrespectively extend alongedges 13 and 1 4. Magnets 21 and 22 have strong magnetic poles at opposite ends thereof on front faces 25 and 26 abutting edges 13 and 14 along outer hemlines 27 and 28; any magnetic poles on the rear faces of magnets 21 and 22, along inner hemlines 29 and 30, are usually so small that they do not overcome gravitational forces. Corresponding magnets 21 and 22 are vertically aligned along the lengths of edges 13 and 14 so that opposite polarity poles of corresponding magnets are in matc hing aligned relationship to provide a seal along the abutting edges 13 and 14. Adjacent ones of magnets 21 and 22 are spaced from each other by a distance sufficient to enable the edges of panels 11 and 12 to remain flexible. Panels 11 and 12 can be fabricated from any suitable type of flexible, non-magnetic material which is easily folded, such as sheets of cloth, mesh or plastic.

When the closure device is closed, outer hemlines 27 and 28 are in abutting relationship to provide a seal for edges 13 and 14. Hemlines 27 and 28 thereby may be considered as defining a boundary for the opening between edges 13 and 14 when theclosure device is opened. The poles faces of magnets 21 and 22 provide magnetic forces that extend across the boundary defined by hemlines 27 and 28, in planes that include or are parallel to the plane of flexible panels 11 and 12. As viewed in FIGS. 2 and 3, the magnetic force from the north pole of magnet 21 extends across hemlines 27 and 28 to the'south pole of magnet 22 while the north pole of magnet 22 extends across the hemlines to the south pole of magnet 21.

Panels 11 and 12 are joined so that the borders have an apex at the upper extremities of the panels so that when the panels are in a full open condition, they are joined at the apex. When panels 11 and 12 are closed, they fall by gravity toward threshold 17 and the uppermost magnet pairs 21 and 22 are attracted toward each other and come into holding contact. The next lower pair of magnets then are attracted toward each other and are brought into holding contact. The process continues, so that generally successive magnets 21 and 22 are brought into abutting relationship, with the magnets closest to the bottom being brought into an abutting relationship at a time most removed from the magnets at the top coming into abutting relationship,

Because the magnetic force is provided through the boundary of the opening defined by hemlines 27 and 28 in planes including or substantially parallel to the plane of panels 11 and 12 the closure of the invention can easily be opened merely by a person kicking at a lower segment of the closure to provide initial access. As the person moves through the closure, the upper segments of the closure part. After the person has moved through the closure, panels 11 and 12 close on each other, regardless of whether panel 11 is in front of panel 12 or vice versa. This is because the magnetic force between magnets 21 and 22 is directed in a plane substantially parallel to panels 11 and 12 and because there is no overlap between the panels, with the panels coming into abutting relationship along outer hemlines 27 and 28.

Magnets 21 and 22 can be inserted into hems 23 and 24 by bonding the rear faces thereof, having relatively weak magnetic poles, to inner hemlines 29 and 30. In the alternative, the permanent magnets can be formed by providing spaced regions of ferrous oxide powder in a plastic binder in hems 23 and 24. The plastic binder is heated to substantially simultaneously coalesce the ferrous oxide powder and bond the powder to hemlines 27-30. Thereafter, opposite polarity magnetic fields are applied to opposite ends of faces 25 and 26 of the fused ferrous oxide powder to form the permanent magnets. The technique of utilizing ferrous oxide powder in a plastic binder with a subsequent fusing action avoids possible problems of magnetic deterioration due to the Curie effect.

While permanent magnets are illustrated as being included in hems 23 and 24, it is to be understood that only one of the hems need include such a permanent magnet and that the other hem may include spaced elements of high magnetic permeability, such as iron slugs. The iron slugs would be positioned in identically the same manner as the correspondingly located perma nent magnets. It is also to be understood that the principles of the invention apply if only one of panels 11 and 12 is flexible, and that the other panel can be relatively rigid. In such an instance, the permanent magnets or elements of high magnetic permeability are positioned on the rigid panel in the same manner as the permanent magnets or elements of high magnetic permeability are located on the flexible panel or an elongated ferrous strip can be provided in the rigid panel. In either case, the magnetic force from the permanent magnet is provided across the boundary in a direction generally parallel to the plane of the rigid panel and theflexible panel when the closure device is closed.

If only one of panels 11 or 12 is flexible, in accordance with a further alternative, the magnetic force in the plane parallel to the fixed and flexible panels can be provided by an elongated permanent magnet strip including magnetized pole faces on opposite faces of the strip. Such a configuration is illustrated in FIGS. 1, 2 and 4 for the horizontally extending portion of the closure device between lower edges 15 and l6'of panels 11 and 12 and threshold 17.

The closure device between threshold 17 and each of edges 15 and 16 is formed by providing an elongated magnetized strip 32 that is mounted in a recess on the upper surface of non-magnetic longitudinally extending, relatively rigid threshold member 33. Strip 32 is magnetized so that the north and south pole faces of the magnet are on opposite faces 34 and 35 of the strip. Thereby, while the closure'device is closed, the pole faces provide a magnetic force component that extends, to a certain extent, in planes including and parallel to the plane of panels 11 and 12. The magnetic force from magnet 32 provides an attractive force for corresponding gapped magnetic elements extending horizontally along the bottom edges 15 and 16 of flexible panels 11 and 12. The gapped magnetic elements along edges 15 and 16, in the embodiment of FIGS. 1, 2 and 4, comprises link chains 36 and 37, which are fabricated of material having high magnetic permeability such as iron. Link chains 36 and 37 inherently provide the flexibility for edges 15 and 16 that is provided by including spaced members of high magnetic permeability in one of hems 23 or 24. Of course chains 36 and 37 inherently provide the necessary air gaps for the magnetic field derived from strip 32 and therefore such a chain can be substituted for the magnets along one of the vertically extending borders.

In operation, after outer seams 27 and 28 have closed so they are in contact throughout their lengths, link chains 36 and 37 contact and are held in situ against the magnetized upper surface 34 of strip 32 to provide complete closure of panels 11 and 12 against threshold 17. Because of the air gap between adjacent links of chains 36 and 37, edges 15 and 16 do not bunch from center line 18 to the points where the edges are pinned to the extremities of threshold 17.

It is noted that outer hemlines 27 and 28 are in abutting relationship throughout their lengths so that there are no airholes in the slit formed between the two outer hemlines. Similarly, no air holes subsist in the slit between the lower edges 15 and 16 and threshold 17. Thereby, the closure device of the present invention is particularly adapted for use with structures in which it is important to prevent relatively small objects, such as insects or flies, from moving through the closure device while it is closed.

In this connection, reference is made to FIG. 5 wherein the closure device illustrated in FIGS. 1-4 is illustrated as the door of a tent 41. The door is comprised of flexible panels 11 and 12 having abutting vertical edges 13 and 14 and horizontally extending lower edges 15 and 16 that are in abutting relationship with the permanent magnet strip 32 that extends along threshold 17. Flexible panels 11 and 12 are sewn at their outer and top edges to a rectangular cutout in tent 41. Thereby, the upper corners of edges 13 and 14 have an apex, along center line 18 at the intersection of the center line with the upper portion of the cutout region of the tent.

The invention can also be employed as a closure device in many other applications. For example, the invention isillustrated in FIG. 6 as a closure device for a garment having a longitudinally extending opening in the vertical direction as defined by the edges of panels 42 and 43. The garment preferably includes a mechanical fastener 44 which initially joins the upper edges of panels 42 and 43 together. After fastener 44 has joined the upper edges of panels 42 and 43 together, the remaining portions of the panels are automatically joined together by the combined forces of gravity and the magnetic forces that subsist across the boundary of the closure, as provided by permanent magnets 21 and 22.

While there have been described and illustrated several specific embodiments of the invention, it will be clear that variations in the details of the embodiments specifically illustrated and described may be made without departing from the true spirit and scope of the invention as defined in the appended claims.

I claim:

l. A closure device for providing access through and closing of an opening of a flexible, non-magnetic panel with equal facility for movement of an object in either direction through the opening, said opening having a boundary defined by a first vertically extending border along the flexible panel and a'second vertically extending border along another member, said first and second borders being in abutting relationship and defining a longitudinal, vertically extending slit while the opening is closed, said panel and member being mechanically joined together at a point on the upper end of the slit, said slit being opened in response to insertion of the object through the slit, said closure device comprising:

vertically extending magnet means running along one of the borders of the slit for establishing a horizontally extending magnetic force across the slit in planes substantially parallel to and including a plane in which the panel lies while the opening is closed, vertically extending magnetic force attractive means running along the other border responsive to the magnetic force for holding the borders in abutting non-overlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, said force establishing means and force attractive means being arranged with said panel, member and slit so that the panel is free to swing in any direction about the point and the panel and member are free to come together solely in response to the force of gravity and the magnetic force, whereby the magnetic force and the force of gravity cause the upper portion of the slit to be initially closed and the lower portion of the slit to be subsequently closed.

2. The device of claim I wherein the magnetic means includes a plurality of spaced permanent bar magnets each having strong opposite polarity magnetic poles on the surface abutting said one border and weak magnetic poles on a surface remote from said one border.

3. The device of claim 2 wherein the magnetic force attractive means includes a plurality of elements spaced from each other in corresponding locations with the permanent magnets, whereby corresponding ones of the permanent magnets and the elements are in substantial abutting relationship with each other while the opening is closed.

4. The device of claim 2 wherein each of the elements is a permanent bar magnet having pole faces on the other border and in alignment with corresponding pole faces of opposite polarity of the bar magnets on said one border.

5. The device of claim 1 wherein said magnet means provides air gaps for magnetic fluc causing the magnetic force.

the surface abutting said one border and weak magnetic poles on a surface remote from said one border.

8. The device of claim 7 wherein the magnetic force attractive means includes a plurality of elements spaced from each other in corresponding locations with the permanent magnets, whereby corresponding ones of the permanent magnets and the elements are in sub stantial abutting relationship with each other while the opening is closed.

9. The device of claim 8 wherein each of the elements is a permanent bar magnet having pole faces on the other border and in alignment with corresponding side pole faces of opposite polarity of the bar magnets on said one border.

10. The device of claim 6 wherein the magnet means includes a permanent magnet having first and second opposite polarity magnetic poles on faces of the magnet adjacent and remote from at least one border 11. The device of claim 10 wherein said panel is flexible and the permanent magnetic means provides air gaps for magnetic flux causing the magnetic force and flexibility for said at least one border.

12. The combination of claim 3 wherein each of the panels has a first horizontally extending border included in a bottom slit for each closed panel, each of the panels being mechanically attached to the remainder of the tent at a location at the end of the bottom slit remote from the vertically extending slit, the tent having a horizontally extending edge defining a second horizontally extending border of the bottom slit, a closure for the bottom slit comprising: horizontally extending magnet means running along one of the borders of the bottom slit for establishing a vertically extending magnetic force across the bottom slit in planes substantially parallel to and including a plane in which the panels lie while the opening is closed, horizontally extending magnetic force attractive means running along the other border of the bottom slit and responsive to the vertically'extending magnetic force for holding the borders of the bottom slit in abutting nonoverlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive means of the borders for the bottom slit having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed, said force establishing means and force attractive means on the borders of the bottom slit being arranged with said panels and bottom slit so that the panels are free to swing in any direction about the pointand the panels are always free to come together solely in response to the force of gravity and the magnetic force.

13. A closure device for providing access through and closing of an opening with equal facility for movement of an object in either direction through the opening, said opening having a boundary defined by: first and second borders of a flexible panel member, a third border along a first member, and a fourth border along a second member, said first and third borders being in abutting relationship and defining a first longitudinal vertically extending slit while the opening is closed, said second and fourth borders being in abutting relationship and defining a second, horizontally extending longitudinal slit while the opening is closed, said slits intersecting substantially at right angles, said panel and first member being mechanically joined together at a first point on the first slit remote from and above the intersection of the two slits, said panel and the second member being mechanically joined together at a second point on the second slit remote from and horizontally to the side of the intersection of the two slits, said slit being opened in response to insertion of the object through the slit, comprising vertically extending first magnet means running along at least one of the borders of the first slit for establishing a horizontally extending magnetic force across the first slit in plane substantially parallel to and including a plane in which the panel lies while the opening is closed, vertically extending magnetic force attractive means in the other border of the first slit responsive to the horizontally extending magnetic force for holding the borders of the first slit in abutting non-overlapping relationship substantially throughout their length, second magnet means in one of the borders of the second slit for establishing a second magnetic vertically extending force across the second slit in planes parallel to and including the panel, and magnetic force attractive means in the other border of the second slit responsive to the second magnetic force for bringing the borders of the second slit in abutting non-overlapping relationship while the borders of the first slit are being brought into abutting relationship by the first magnet means, said first magnetic force establishing means and the force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, and said second magnetic force establishing means and the second magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, both said first and second magnetic force establishing means and the first and second magnetic force attractive means being arranged with said panel, members and slits so that the panel is free to swing in any direction about the point and the panel and member are free to come together solely in response to the force of gravity and the magentic force, whereby said panel initially closes the vertically extending slit in proximity to the first point while the second slit is being closed in proximity to the second point and thereafter the first slit is closed by the lower portions of the first slit coming into contact with each other while the portions of the second slit remote from the second point are coming into contact with each other.

Page 1 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,827,019 Dated Joly 30, 1974 Inventor(s) Gideon r u It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

Column 1, line 16, change "buttoms" to -buttons line 25-26, change "matc hing" to --match-ing--.

Column 5, line 24; change "magnetic" to -magnet--.

IN THE CLAIMS:

Column Z, line 56 change "fluc" to -flux-. Column '7, li 65 after "along", insert --one of the borders of the slit-for establishing a horizontally extending magnetic force across the slit in planes substantially parallel to and including a plane in which the panels lie while the opening is closed, vertically extending magnetic force attractive means running along the other border responsive to the magnetic force for holding the borders in abutting non- (cont'd) :ORM P0405) $69) USCOMM-DC scans-Pee U.$. GOVERNMENT PRINTING OFFICE 1969 O-366-334 Page 2 UNITED- STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,827,019 Dated July 30, 1974 Inventor(s) Gideon lf u It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

overlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive "means having substantially abutting Surfaces that are freely slidable with respect to each other as the opening is being closed, said force establishing means and force attractive means. being arranged with said panels and slit so that the panels are free to swing in any direction about the point and the panels are free to come together solely in response to the force of gravity and the magnetic force, whereby the magnetic force and the force of gravity cause the upper portion of the slit to be initially closed and the lower portion of the slit to be subsequently closed.- Column s, line 15 delete "side".

Column 8, line 25 change "3" to 6-.

line 9, change "plane s" to --planes--;

(Cont'd) l OR PO-IOSO (10-69) USCOMM-DC 6376-P69 U.S. GOVERNMENT PRINTING OFFICE 4 I969 0-366-334 Page 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,827,019 Dated July 30, 1974 ln-ventofls) Gideon P. Serbu It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 13, column 10, line 1, before "force" insert -first magnetic-;

column 10, line 16, change "magentic" to -magnetio--.

Signed and sealed this 1st day ofApril 1975.

(SEAL) Attest:

" C. MARSHALL DAN-N RUTH *C. MASON Commissioner of Patents Attesting- Officer I and Trademarks FORM PCO-1 (10 69) USCOMM-DC 60376-P69 v U 5. GOVERNMENT PRlNTlNG OFFICE I969 0-73S6-3SA 

1. A closure device for providing access through and closing of an opening of a flexible, non-magnetic panel with equal facility for movement of an object in either direction through the opening, said opening having a boundary defined by a first vertically extending border along the flexible panel and a second vertically extending border along another member, said first and second borders being in abutting relationship and defining a longitudinal, vertically extending slit while the opening is closed, said panel and member being mechanically joined together at a point on the upper end of the slit, said slit being opened in response to insertion of the object through the slit, said closure device comprising: vertically extending magnet means running along one of the borders of the slit for establishing a horizontally extending magnetic force across the slit in planes substantially parallel to and including a plane in which the panel lies while the opening is closed, vertically extending magnetic force attractive means running along the other border responsive to the magnetic force for holding the borders in abutting non-overlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, said force establishing means and force attractive means being arranged with said panel, member and slit so that the panel is free to swing in any direction about the point and the panel and member are free to come together solely in response to the force of gravity and the magnetic force, whereby the magnetic force and the force of gravity cause the upper portion of the slit to be initially closed and the lower portion of the slit to be subsequently closed.
 2. The device of claim 1 wherein the magnetic means includes a plurality of spaced permanent bAr magnets each having strong opposite polarity magnetic poles on the surface abutting said one border and weak magnetic poles on a surface remote from said one border.
 3. The device of claim 2 wherein the magnetic force attractive means includes a plurality of elements spaced from each other in corresponding locations with the permanent magnets, whereby corresponding ones of the permanent magnets and the elements are in substantial abutting relationship with each other while the opening is closed.
 4. The device of claim 2 wherein each of the elements is a permanent bar magnet having pole faces on the other border and in alignment with corresponding pole faces of opposite polarity of the bar magnets on said one border.
 5. The device of claim 1 wherein said magnet means provides air gaps for magnetic flux causing the magnetic force.
 6. A closure for an opening of a pair of flexible panels of a tent, said panels having first and second mating borders defining a vertically extending slit when the panels are closed, said panels being mechanically joined together at a point on the upper end of the slit, said closure device comprising; vertically extending magnet means running along one of the borders of the slit for establishing a horizontally extending magnetic force across the slit in planes substantially parallel to and including a plane in which the panels lie while the opening is closed, vertically extending magnetic force attractive means running along the other border responsive to the magnetic force for holding the borders in abutting nonoverlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed, said force establishing means and force attractive means being arranged with said panels, and slit so that the panels are free to swing in any direction about the point and the panels are free to come together solely in response to the force of gravity and the magnetic force, whereby the magnetic force and the force of gravity cause the upper portion of the slit to be initially closed and the lower portion of the slit to be subsequently closed.
 7. The device of claim 6 wherein the magnet means includes a plurality of spaced permanent bar magnets each having strong opposite polarity magnetic poles on the surface abutting said one border and weak magnetic poles on a surface remote from said one border.
 8. The device of claim 7 wherein the magnetic force attractive means includes a plurality of elements spaced from each other in corresponding locations with the permanent magnets, whereby corresponding ones of the permanent magnets and the elements are in substantial abutting relationship with each other while the opening is closed.
 9. The device of claim 8 wherein each of the elements is a permanent bar magnet having pole faces on the other border and in alignment with corresponding pole faces of opposite polarity of the bar magnets on said one border.
 10. The device of claim 6 wherein the magnet means includes a permanent magnet having first and second opposite polarity magnetic poles on faces of the magnet adjacent and remote from at least one border.
 11. The device of claim 10 wherein said panel is flexible and the permanent magnetic means provides air gaps for magnetic flux causing the magnetic force and flexibility for said at least one border.
 12. The combination of claim 6 wherein each of the panels has a first horizontally extending border included in a bottom slit for each closed panel, each of the panels being mechanically attached to the remainder of the tent at a location at the end of the bottom slit remote from the vertically extending slit, the tent having a horizontally extending edge defining a second horizontally extending border of the bottom slit, a closure for the bottom slit comprising: horizontally extending Magnet means running along one of the borders of the bottom slit for establishing a vertically extending magnetic force across the bottom slit in planes substantially parallel to and including a plane in which the panels lie while the opening is closed, horizontally extending magnetic force attractive means running along the other border of the bottom slit and responsive to the vertically extending magnetic force for holding the borders of the bottom slit in abutting non-overlapping relationship substantially throughout their length, both said magnetic force establishing means and said magnetic force attractive means of the borders for the bottom slit having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed, said force establishing means and force attractive means on the borders of the bottom slit being arranged with said panels and bottom slit so that the panels are free to swing in any direction about the point and the panels are always free to come together solely in response to the force of gravity and the magnetic force.
 13. A closure device for providing access through and closing of an opening with equal facility for movement of an object in either direction through the opening, said opening having a boundary defined by: first and second borders of a flexible panel member, a third border along a first member, and a fourth border along a second member, said first and third borders being in abutting relationship and defining a first longitudinal vertically extending slit while the opening is closed, said second and fourth borders being in abutting relationship and defining a second, horizontally extending longitudinal slit while the opening is closed, said slits intersecting substantially at right angles, said panel and first member being mechanically joined together at a first point on the first slit remote from and above the intersection of the two slits, said panel and the second member being mechanically joined together at a second point on the second slit remote from and horizontally to the side of the intersection of the two slits, said slit being opened in response to insertion of the object through the slit, comprising vertically extending first magnet means running along at least one of the borders of the first slit for establishing a horizontally extending magnetic force across the first slit in planes substantially parallel to and including a plane in which the panel lies while the opening is closed, vertically extending magnetic force attractive means in the other border of the first slit responsive to the horizontally extending magnetic force for holding the borders of the first slit in abutting non-overlapping relationship substantially throughout their length, second magnet means in one of the borders of the second slit for establishing a second magnetic vertically extending force across the second slit in planes parallel to and including the panel, and magnetic force attractive means in the other border of the second slit responsive to the second magnetic force for bringing the borders of the second slit in abutting non-overlapping relationship while the borders of the first slit are being brought into abutting relationship by the first magnet means, said first magnetic force establishing means and the first magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, and said second magnetic force establishing means and the second magnetic force attractive means having substantially abutting surfaces that are freely slidable with respect to each other as the opening is being closed and opened as the object moves through the opening, both said first and second magnetic force establishing means and the first and second magnetic force attractive means being arranged with said panel, members and slits so that the panel is free to swing in any direcTion about the point and the panel and member are free to come together solely in response to the force of gravity and the magnetic force, whereby said panel initially closes the vertically extending slit in proximity to the first point while the second slit is being closed in proximity to the second point and thereafter the first slit is closed by the lower portions of the first slit coming into contact with each other while the portions of the second slit remote from the second point are coming into contact with each other. 